Understanding the Role of Dopant Metal Atoms on the Structural and Electronic Properties of Lithium-Rich Li1.2Ni0.2Mn0.6O2 Cathode Material for Lithium-Ion Batteries

Improving the stability of lithium-rich cathode materials is important in refining the overall performance of lithium-ion batteries. Here, we have proposed doping of different metal atoms such as K⁺, Ca²⁺, Cd²⁺, and Al³⁺ in different sites of Li_1.2Ni_0.2Mn_0.6O₂, and we have investigated their structural and electronic properties using first-principles calculations. We found that the Ni ions in the pristine Li_1.2Ni_0.2Mn_0.6O₂ structure maintained the +3 oxidation state for a longer time and resulted in the structural deformation during the long cycling process. Whereas, the Ni ions in the Cd-, K-, and Ca-doped Li_1.2Ni_0.2Mn_0.6O₂ structure are in the +3 oxidation state for a very short time, compared to the pristine system. Our density functional theory (DFT) results show that the doping of the Cd ion in the Ni site of Li_1.2Ni_0.2Mn_0.6O₂ is the most suitable one, because it inhibits structural change, decreases the formation energy, and suppresses the Jahn-Teller distortion, compared with the pristine system and other dopant atoms. This theoretical study gives new insight about doping strategy and will help in improving the electrochemical performance of Li-rich cathode materials.

Methanol decomposition reactions over a boron-doped graphene supported Ru–Pt catalyst

In-depth investigations of adsorption and decomposition of methanol over boron-doped graphene supported Ru–Pt catalyst are presented using periodic density functional theory calculations. Methanol decomposition on such catalyst proceeds through formation of methoxide (CH₃O) and via stepwise dehydrogenation of formaldehyde (CH₂O), formyl (CHO), and carbon monoxide (CO).

Improved Interfacial Properties of MCMB Electrode by 1-(Trimethylsilyl)imidazole as New Electrolyte Additive To Suppress LiPF6 Decomposition

Trace water content in the electrolyte causes the degradation of LiPF₆, and the decomposed products further react with water to produce HF, which alters the surface of anode and cathode. As a result, the reaction of HF and the deposition of decomposed products on electrode surface cause significant capacity fading of cells. Avoiding these phenomena is crucial for lithium ion batteries. Considering the Lewis-base feature of the N-Si bond, 1-(trimethylsilyl)imidazole (1-TMSI) is proposed as a novel water scavenging electrolyte additive to suppress LiPF₆ decomposition. The scavenging ability of 1-TMSI and beneficiary interfacial chemistry between the MCMB electrode and electrolyte are studied through a combination of experiments and density functional theory (DFT) calculations. NMR analysis indicated that LiPF₆ decomposition by water was effectively suppressed in the presence of 0.2 vol % 1-TMSI. XPS surface analysis of MCMB electrode showed that the presence of 1-TMSI reduced deposition of ionic insulating products caused by LiPF₆ decomposition. The results showed that the cells with 1-TMSI additive have better performance than the cell without 1-TMSI by facilitating the formation of solid-electrolyte interphase (SEI) layer with better ionic conductivity. It is hoped that the work can contribute to the understanding of SEI and the development of electrolyte additives for prolonged cycle life with improved performance.

First principles study of organic sensitizers for dye sensitized solar cells: effects of anchoring groups on optoelectronic properties and dye aggregation

Efficient organic sensitizers with improved spectral properties and less aggregation have been proposed for practical DSSCs based on theoretical calculations.